Tyan's Thunder K7 S2462, dual MP with on-board U160 although I don't think it's zero-RAID. Which means if you want to run some serious RAID you better buy mobo without SCSI controller, as most RAID controllers are already equipped with SCSI controller.
S2462 is unfortunately $400+.
My suggestion, built your server on some inexpensive Intel board bought from overstock selling merchant, and keep your Athlon for gaming and running applications .
E.g. you can get Thunder 2500 (dual p3/slot1 w/dual chann U160/Serverworks III HE chipset/64bit PCI) for $199 at computersurplusoutlet.com. Plug couple P3s, and you have extremely stable server (up to 8GB SDRAM) for not too much money.
Then, after you bled for your SCSI drives, built your ultimate gaming/video/photo processing machine around single XP.